Method of and means for controlling low temperature refrigerants



Jun 9, 1936. w. F. BAIRD 2343,76?

METHOD OF AND MEANS FOR CONTROLLING LOW TEMPERATURE REFRIGERANTS FiledNqv. 'r, 1931 2 Sheets-Sheet 1 2 Sheets-Sheet 2 W. F. BAIRD Jun & ma.

METHOD OF AND MEANS FOR CONTROLLING LOW TEMPERATURE REFRIGERANTS Filed Nov. 7, 1931 Patented June 9, 1936 PATENT OFFICE ME'I'lIOD OF AND- MEANS FOR CON- TROLLING LOW FRIGERANTS TEMPERATURE RE- William F. Baird, Lexington, Mass. Y Application November '1, 1931, Serial No. 573,531

19 Claims.

This invention relates to apparatus for controlling the transfer of heat from a refrigerator cabinet to a primary refrigerant. The invention relates more particularly to apparatus for the control of the refrigerating effect of refrigerants having the temperature far below the temperature desired for the refrigerator cabinet. This application is a continuation in part of the applicants application Serial No. 343,958, filed March 2nd, 1929. Apparatus for the same general purpose as the present invention is described in my co-pending applications Serial No. 412,247, filed December 6, 1929, issued as Patent No. 1,923,472, August 22, 1933, and Serial No. 470,945,

filed July 26 1930 issued as Patent No. 1,990,219,

February 5, 1935 and also in a patent to Gase and Seymer No. 1,371,235. In general, apparatus of this type consists essentially of a gas-tight system, hereinafter referred to as a condensenhav- 2o ing a portion of its external area exposed directly to the interior of a refrigerator cabinet, and another portion of its exterior surface exposed to the chilling action of a low temperature refrigerant, such for example as solid carbon dioxide or liquid 25 air. Since liquid air and other similar refrigerants are at present commercially out of the question by reason of cost, the embodiment of the invention hereinafter described is designed particularly for use with solid carbon dioxide, but it is understood that similar apparatus may be suit- "ably modified for use with other low temperature primary refrigerants. The gas-tight condenser, which may be embodied in various forms or shapes, contains a volatile liquid or liquids'which are capable of transferring the heat rapidly by evaporating against the warmest surface of the fcondenser and condensing on the chilled surace.

In using low-temperature refrigerants, such as solid carbon dioxide, for the chilling of refrigerator cabinets, there are three conditions which must be met in order to obtain satisfactory service. First, the apparatus must be such as will maintain the cabinet substantially at the desired temperature when the'temperature of the outside atmosphere is at the maximum value which is liable to be encountered in actual service. Second, the apparatus should be such that excessive chilling of the refrigerator cabinet is avoided when thew-outside atmosphere is ata minimum. This condition of course depends on the atmospheric temperature being above that desired for the interior of the cabinet. Third. the apparatus should be sensitive so as to respond quick y to casual introduction of heat, as by the opening of a door or the insertion of warm products into the cabinet so that when the cabinet temperature is raised by such introduction of heat, the temperature is quickly restored to the desired level. Apparatus of this type, in some cases, maybe designed according to correct general principles and may operate satisfactorily over a limited range of temperatures, but may fail to function satisfactorily in response to temperatures beyond such range. This may be due to any one or more of a number of causes, but is usually due to the failure of some part of the apparatus to transfer heat at a sufliciently high rate to take care of the inflow from the outside atmosphere. According to the present invention. various improvements are made in apparatus of this type tending to widen materially the range of satisfactory operation of the apparatus and to render the apparatus more eflicient in maintaining a substantially constant predetermined temperature level in the refrigerator cabinet.

The flow of heat from the refrigerator cabinet to the'primary refrigerant, in apparatus of this type, is as follows. The heat is absorbed by the external surface portion of the condenser which is exposed to the air within the cabinet. This heat passes by conduction through the wall of the condenser and is transferred to any of the liquid within the condenser which may be in contact with such portions of the wall. The heat entering the volatile liquid promotes evaporation thereof, the heat thus being carried off by the more active molecules of liquid which escape in the form of vapor. These energized vapor molecules quickly traverse the space between the warmer portion of the condenser and the chilled portion, and impinge on the latter portion, giving up heat energy in the course of being condensed into liquid or solid form. This heat energy is transferred by conduction through the wall of the condenser and through any layer of solidified liquid which may be formed on the surface of the wall, the heat then being transferred to the primary refrigerant which absorbs the same in the process of vaporization either from the liquid form as in the case of liquid air, or from the solid form as in the case of carbon dioxide. The present invention relates to improvements in heatconducting apparatus of this type,. these improvements being designed to facilitate the trans.- fer of heat at the points where in other forms of apparatus the transfer is often impeded by structural limitations. present invention, the transfer of heat from the refrigerator cabinet into the liquid is more efficiently accomplished, and improved means of transfer of heat from the wall of the condenser to the primary refrigerant are shown and described.

In order to operate satisfactorily, it is desirable that the solid carbon dioxide be enclosed in an insulated container, the floor of which is identical with or in intimate thermal contact with a portion of the upper part or ceiling of the condenser. For simplicity and compactness, the condenser Thus, according to the tion of the ceiling of the box which serves as a bottom for the CO2 container is preferably insulated so as to reduce the inflow of heat by conduction to a minimum. Thus the flow of heat from the air within the cabinet to the primary refrigerant is substantially confined to transfer by the vapor from the liquid contained in the condenser. The bottom or floor of the condenser is, according to the present invention, so constructed as to facilitate the transfer of heat from the refrigerator cabinet space into the liquid within the condenser. As is hereinafter described more in detail, the cabinet temperature is predetermined by the selection of a liquid of suitable characteristics including a freezing point at or near a certain value determinable by calculation, and by the use of a predetermined quantity of liquid within the condenser such that when the cabinet is substantially at the desired temperature, the entire quantity of liquid is in the form of a frozen layer on the chilled portion of the ceiling of the condenser. In such case, there is an appreciable transfer of heat across the condenser by radiation. This transfer by radiation may be sufiicient to take care of the inevitable inflow of heat through the walls of the refrigerator cabinet, especially when such inflow is small,

as in cold weather. In any event, a slight rise of temperature in the cabinet increases the radiation sufficiently to melt a small amount of the frozen secondary refrigerant which drips and vaporizes to carry the extra heat rapidly across the interior of the condenser. Thus, when a certain liquid has been selected for use in the condenser, the temperature at which the cabient will be maintained may be determined within a reasonable range by the quantity of liquid sealed up in the condenser.

In actually constructing apparatus to embody the present invention,- use is made. of the well known equation for heat transfer as follows:

, where H equals B. t. u./hr. passing through a given body, such, forv example, as the layer of solidified secondary refrigerant formed on the chilled portion of the ceiling,

K=B. t. u./hr./inch of thickness/sq. ft./degree F.,

T1=temperature of warmer surface of the mass,

T2=temperature of colder surface of the mass,

A=conducting area of mass,

D=linear dimension of mass in the direction of heat ficw.

- erant, the actual value of T2 depending upon the efliciency of heat transfer from the bottom-of the Cog-container to the CO2 itself. The value of A, that is, the area of the chilled surface, should be sufliciently large to take care of the maximum heat fiow which may enter the condenser from the cabinet when D is. at its maximum value.

According to one embodiment of the invention hereinafter described, the floor of the condenser is so arranged as to promote an eiiicient used is determined empirically as follows.

distribution of condensate dripping from the chilled ceiling over its entire surface. It is obvious that for maximum efiiciency of transfer of heat from the cabinet to the liquid, the entire floor of the condenser should be wetted so that the entire area of the floor is used in direct transfer of heat therefrom to the liquid. In designing apparatus according to the present invention, a condenser is constructed having as large a fioor area as is conveniently possible for the cabinet to be chilled. The amount of secondary refrigerant The apparatus is set up with the carbon dioxide container filled with solid CO2. A non-freezable liquid, preferably of approximately the same vapor pressure as available suitable freezable liquids, is inserted in the condenser, all the air and other inert gases being removed so as to leave the condenser with substantially nothing but the liquid and its vapor. When the system has reached an equilibrium, the cabinet temperature is noted. More non-freezable liquid is introduced into the condenser and the effect on the equilibrium temperature of the cabinet is again noted. When a further addition of non-freezable liquid fails to result in a lower cabinet temperature, the quantity then in the condenser, minus the last amount addexperiment has a freezing point lower than that of the carbon dioxide. When a freezable liquid, that is, one having a freezing point above that of the carbon dioxide, is introduced into the condenser in place of the non-freezable liquid, an extra quantity must be allowed for a layer of frozen liquid which will remain on the ceiling of the condenser even when maximum heat flow passes through the condenser. In other words, the actual amount of secondary refrigerant to be sealed up in the condenser will be sufilcient to wet the entire floor of the condenser and to provide' the minimum frozen layer on the chilled portion of the ceiling. In selecting a suitable freezable liquid for use as a secondary refrigerant in the condenser, use may be made of the formula hereinbefore given. The approximate quantity of liquid to be used being known,'the value of A and D can be easily calculated. 'The value 'of K can be determined either experimentally or from tables giving the characteristics of well known liquids. The value of T2 can be taken as slightly above the temperature of the solid carbon dioxide. H depends on the'refrigerating requirements of any particular refrigerator cabinet and is thus determined by figuring the maximum rate at which the condenser can absorb heat from the cabinet when the cabinet is somewhat above the desired equilibrium temperature The equation can then be solved for T1 to obtain the optimum freezing point of the liquid to be selected as a secondary refrigerant. Since the value of D will depend upon the characteristics of the liquid chosen, it may be necessary to recalculate the desired value of T1 after the first rough calculation and a subsequent correction of the value of D. If a liquid can be found with a freezing point approximately equal to the calculated value of T1, and with other characteristics such as the vapor pressure approximately similar to the non-freezable test liquldpreviously employed, a suitable quan- 75 tity of this liquid, measured according to the preliminary test hereinbefore described, will maintain the cabinet at a temperature very close to the desired equilibrium temperature. For example, in the case of a motor truck body built for transporting ice cream or other frozen food, stufls, the temperature at or near zero degrees F. is desirable. Within a truck body of ordinary size, a refrigerating apparatus including a condenser approximately 36 inches square can be accommodated. With a condenser of this size, a quantity of approximately one pint of anon-freezable liquid such as ether or methyl alcohol is found to be the minimum amount which will give maximum heat transfer, that is, which will efllciently wet the entire floor surface of the condenser. A first calculation for the optimum freezing point of freezable liquid to be substituted for the ether gives 75 F. While there are several known liquids having freezing points'near this value, such liquids for the most part are objectionable for one reason or another, mostly on account of high cost, so that the choice of liquids is limited as a practical matter. Hence it may be necessary to select a liquid having a freezing point either below or above the optimum value. If a liquid such as chloroform is selected with a freezing point below this optimum value, it will be necessary to use less of the liquid as otherwise the equilibrium temperature of the cabinet would be too low. The use of such a liquid is objectionable since the reduced quantity required results in inefficiency in wetting the floor of the condenser. If a liquid such as carbon tetrachloride be used having a freezing point higher than the optimum determined value, more of this liquid must be'used. The use of such liquid is open to the objection that the temperature T1 is thereby raised and the maximum over-all capacity of the condenser for heat transfer is correspondingly reduced. ,Con-

sequently, it is sometimes advantageous to use a mixture of two or more liquids which mutually alter each others freezing point. A limited amount of suitable non-freezable liquid may also be included in the mixture, if desired, as it will be largely, if not wholly, occluded in the mass formed by congealing the freezable ingredients of the mixture against the ceiling of the condenser.

It is an object of the present invention to provide apparatus which is more sensitive to variations of cabinet temperature and which has greater heat-transferring capacity than any previous apparatus of equal size. ratus hereinafter described is designed for and capable of a relatively large flow of heat therethrough for a given temperature difference between the air,of the cabinet and the solid carbon dioxide, and which effectively insulates the carbon dioxide from the air of the cabinet when the latter is at the desired cabinet temperature;

so that in the latter case, only a very slight transfer of heat occurs by unavoidable conduction and radiation. This prevents undesirably low temperatures in the cabinet ang also economizes on the consumption of the soli carbdn dioxide.

Among the novel features of structure by which improved efliciency is obtained, is the provision of means for effectively distributing the condensed secondary refrigerant which drips from the ceiling of the condenser, over the entire floor area of the condenser. To this end, the floor of the condenser is preferably constructed with its high point at the center, the floor sloping away from the high point in all-directions to its periphery.

For max mum efflciency of heat transfer through To this end, the appathe condenser, a thin film of condensate should be kept flowing over as much of the floor of the condenser as it will cover. The motion of the liquid over the floor materially aids heat transfer from the floor to the liquid. The spreading of the liquid over as much of the area of the floor as possible utilizes as much as possible of the conducting capacity of the floor itself. It is evident that portions of the floor which are not wettedjby the con densate are substantially useless since the. conductionof heat along the floor in comparison with the conduction through the floor is negligible. For

effective distribution of the condensate over the condenser floor, it is likewise important that the condensate which forms against the central portion of the ceiling of the condenser be dripped from this portion of the ceiling and not be allowed to trickle along the ceiling to the side walls of the condenser. This is particularly important in the case of installations in vehicles such as motor trucks, since such vehicles are subject to frequent tilting due to irregularities and camber of the roads over which they travel. The invention therefore includes the provision of structure designed to ensure the dripping of condensate on the central portion of the floor in spite of casual tilting of the condenser. The distribution of the condensate over the floor of the condenser may be aided, according to the invention, by suitable structure which has the effect of scattering any condensate which otherwise might tend to flow in a narrow stream from the center of the floor to the boundary thereof. Various means of accomplishing this result are hereinafter described. The uniform distribution of condensate over the floor of the condenser is furthermore advantageous since it permits the use of a minimum amount of secondary refrigerant in the condenser, thereby normally preventing accumulations of condensate in the condenser with resulting hydrostatic pressures which tend to raise the boiling point of the condensate and thus to diminish the over-all efflciency of the condenser. Furthermore, by using a minimum amount of secondary refrigerant, not only is economy effected in the materials required for the refrigerating unit, but also there is an added sensitivity of action in the condenser due to the small amount of secondary refrigerant, the temperature of which must be raised in order to promote vaporization by contact with the floor of the condenser. Incidentally, it is desirable in this connection to employ a second refrigerant having as low a specific heat as possible.

According to the present invention, improved means are provided for facilitating the transfer of heat from the floor of the container for solid carbon dioxide to the block of carbon dioxide itself. Solid carbon dioxide sublimates at atmospheric pressures from the solid state directly to the gaseous state. As a result, a block of solid carbon dioxide is ordinarily bathed in a film of gaseous carbon dioxide which is an efiicient nonconductor of heat. For example, when a block of solid carbon dioxide rests on a plane metal surface, the block is almost supported clear of the metal by the fllm of gas formed at the bottom invention, reference may be had to the description of certain embodiments thereof which follows, and to the illustration thereof on the drawings, of which,-

Figure 1 is a sectional view of the refrigerator cabinet embodying the invention.

Figure 2 is a detailed section of a portion of Figure 1 on a larger scale.

Figure 3 is a fragmentary perspective view, partly in section, of a portion of the apparatus illustrated in Figure l.

Figure 4 is a fragmentary perspective view of a modified form of part of the apparatus shown in Figure 3.

Figure 5 is a fragmentary perspective view of another modification.

Figure 6 is a fragmentary perspective end view of a modified form of condenser.

Figure 7 is a fragmentary perspective view of -a portion of Figure 6 on a larger scale.

Figure 8 is a transverse sectional view of an other embodiment of the invention.

Figure 9 is a plan view of the condenser shown in Figure 8, a portion of the top being broken away to show the interior construction.

Figure 10 is a section on the line l|0 of Figure 9.

' Figure 11 isa fragmentary sectional view of a refrigerator showing a mechanical distributing device.

' Figure 12 is a section on the line i2l2 of Figure 11.

condenser 2!! installed in the upper portion of a refrigerator cabinet 2 I. The particular embodiment of the invention illustrated in Figure 1, as described, is of a size suitable for refrigerating motor truck bodies. The condenser 20 may therefore have a width of about 36 inches and about the same length, although in some cases the length will be greater. The top or ceiling 22 of the condenser is preferably plane, the bottom 23 being preferably curved in such a manner that it slopes away in all directions from a central high point 24 to the sides of the condenser. The floor 23 may conveniently have the shape of a portion of a sphere of about 75 inches radius, although the invention is not limited to any particular shape of floor, the important characteristic being that the fioor slopes away from the central point 24 toward the sides of the condenser. With a floor 23 having a spherical curvature on a radius of '75 inches, if the center point 24 is about one inch below the ceiling 22, the floor at the sides of the condenser will be about three inches below the ceiling. The central portion 25 of the ceiling 22 serves as the fioor for a container 26 for primary refrigerant. Since the only low temperature refrigerant which can now be produced at a sufliciently low price to be commercially available is solid carbon dioxide, the container 26 is preferably, as hereinafter described, designed for use with this particular refrigerant. The side walls of the container 26 are well insulated and are pref rably a p Of the construction of the refrigerator body 2|. A removable hatch cover 30 is provided to close the top of the container and to be removed for the insertion of fresh refrigerant. In order to promote the heat flow from the container floor 25 into a block 3| of solid carbon dioxide, a series of parallel fins 32 are secured to or integral with the floor 25. As indicated in Figure 3, these fins may be conveniently supplied in the form of channeled members which may be welded, soldered, or otherwise aflixed to the floor 25 in side by side relation so that the upstanding sides of the channels constitute the fins 32. The block 3| of solid carbon dioxide'is adapted to rest on the upper edges of these fins. As shown, the fins are of substantial thickness so as to be capable of conducting a substantial volume of heat fiow from the fioor 25 of the container. In the ordinary use of a refrigerator of the type described, the supply. of heat to the fins 32 is sufficient in volume to cause relatively rapid sublimation of the solid carbon dioxide where the block comes in contact with the upper edges of the fins. Thus parallel channels are formed in the bottom of the block and the tongues of solid carbon dioxide between these channels project downwardly until they come in contact with the floor 25 of the provision must be made for the ready escape of gaseous carbon dioxide which is sublimed from the bottom of the block. To this end, the tops of the fins 32 are widened as at 33 to form beads or rails which are wider than the lower portions of the fins 32. Hence under each overhanging portion of the beads 33 channels are provided for the escape of CO2 gas between the sides of the fins 32 and the adjacent tongues of solid carbon dioxide projecting down between the fins.

This structure, in addition to being highly efiec- 35 tive in promoting heat flow from the fioor of the container to the carbon dioxide itself, is easily cleaned. This is an important practical feature since commercial solid carbon dioxide contains impurities which in time form a heat-retarding layer at the bottom of the container. Instead of the U-shaped channel members shown in Figure 3, individual fins may be formed as in Figure 4 or in other equivalent shapes, and may be secured to the floor 25 as hereinbefore described. Another row supporting platforms 35 separated by lower floor portions 36, the floor portions 35 and 36 being connected by side walls 31 which are preferably at an angle such that the upper floor portions 35 partly overhang the lower floor portions 36. This construction thus ensures adequate channels for the escape of CO2 gas from the bottom of the block. The gas which is produced by the sublimation of solid CO2 is very cold at first and hence has a certain amount of refrigerating value in spite of its relatively low specific heat. This refrigerating value may be largely conserved by causingthe gas formed in the container to flow out therefrom through a copper pipe 36. A considerable length of this pipe, conventionally shown on the drawings as a coil 39, is suitably arranged in the upper part of tle cabinet to assist in the chilling of the air therein, the temperature of the cold gas within the pipe 39 being raised until the gas is finally discharged into the open atmosphere at a temperature nearly that of the air in the cabinet.

As hereinbefore stated, the floor 25 of the container for refrigerant is preferably identical with the central portion of the ceiling 22 of the condenser. This central portion 25 thus constitutes the condensing area of the inner surface of the condenser 20. Since the refrigerator herein described is. intended for use on a motor truck or other vehicle, it is desirable that the condensate which is formed on the condensing surface 25 be dripped from this portion of the ceiling and that it be prevented from trickling along the ceiling to a side wall of the condenser when the vehicle is tilted. To ensure dripping of the condensate on the portion of the floor of the condenser immediately below the condensing surface 25, I may secure to the condensing surface a series of rows moved, leaving thevertical wires in side by side spaced relation projecting from the surface 25 in rows. Thus condensate whichforms on the condensing surface 25 runs down the nearest wires 4|] and drips from the lower ends thereof.

Enclosed within the condenser 2|] is a suitable quantity of secondary refrigerant adapted to vaporize when in contact with the floor 23 of the condenser and to condense against the condensing surface 25. This secondary refrigerant, which is utilized to transfer heat by vaporization from the floor of the condenser to the condensing surface 25, is preferably a liquid ormixture of liquids which have a freezing point somewhat higher than that of carbon dioxide. Before sealing ofi the condenser 20, the air and other non-condensible gases therein are removed as completely as possible, leaving within the condenser nothing but the secondary refrigerant which may be in any one or more of its phases, gaseous, liquid and solid. The quantity of secondary refrigerant which is sealed up in the condenser 20 is preferably such that when the interior of the cabinet 2| reaches the desired equilibrium temperature (say, zero degree Fahrenheit) all of the secondary refrigerant will be congealed in a solid layer against the surface 25 and none of it will be in liquid form.

When the refrigerator is in such a condition, there is inevitably a certain amount of heat flow to the solid carbon dioxide by reason of radiation and conduction. The radiation cannot be avoided, though it might be reduced by polished interior surfaces in the condenser. It is important, however, that the flow of heat by conduction to the primary refrigerant be reduced to the minimum. To this end, the ceiling or top 22 of the condenser, which must be of substantial thickness for sufficient mechanical strength, is interrupted by a gap 4| which extends around the condensing portion 25 of the ceiling. In order to preserve the gas-tight character of the condenser 20, the gap 4| is bridged by a strip 42 of thin metal, the edges of which are soldered or welded to the outer surfaceof the top 22. Beneath the strip 42, I may lay a strip 43 of canvas'or the like to support the portion of the thin strip 42 between its soldered edges away from the ceiling. The gap 4| serves as an effective barrier against conduction of heat from the sides of the condenser 20 to the central portion of the ceiling 22, and the amount of heat conducted across the substantial width of the thin strip 42 is slight. Since the condenser 20 is of substantial length and width and must support a considerable external pres-- sure, it is necessary to shore the bottom 23 by means of a number of posts 45 extending from the ceiling to the bottom. The foot of each of these posts preferably rests on an insulating pad. of leather or other suitable insulating material. On the floor 23 of the condenser, means is preferably provided for ensuring the uniform distribution thereover of condensate which drips from the condensing surface 25. To this end, I may lay on the floor 23 a ,layer of easily pervious material such as copper wire screening 45. In order to hold this screening in close uniform contact with the entire area of the floor, I'may impose thereon a layer 41 of steel wool or the like over which a second layer 48 of screening is laid. The pads 46 beneath the posts 45 press against the upper screening 48 and thus hold the lower screen 46 smoothly against the surface of the floor 23. The screen and steel wool thus serve to spread the flow laterally so that there is substantially uniform distribution of the condensate over. the floor of the condenser. In order to facilitate the transfer of heat from the air within the cabinet 2| to the bottom of the condenser 20, the surface area of this bottom may be greatly increased by the use of fins 49 of substantial thickness to aid in the conduction of heat to the floor 23 of the condenser, these fins being arranged on the bottom of the condenser in any suitable pattern. In the embodiment illustrated in Figures 1 and 2,

these fins extend in a star pattern from the center by means of reverse bends in the metal sheet composing the floor, these bends forming narrow channels 53, as shown in Figure '7. In order to permit the secondary refrigerant access to the entire surface of thesheet constituting the floor, the walls of each channel 53 are separated as by a strip of copper netting 54, the lower edge of each strip resting on the bottom of a channel 53. its upper edge projecting above the floor level of the condenser. When the condenser is evacuated, the low-pressure sucks together the side walls of each channel 53, but the strips of netting 54 prevent complete collapse of these channels and keep them sufliciently open to receive small quantities of secondary refrigerant. This form of condenser is very efficient since it provides a large floor surface capable of being wetted by secondary refrigerant which is separated from the air within the cabinet solely by the thickness of the metal constituting the floor itself. The interior details of the condenser 50 are not illustrated in Figure 6, a portion of the exterior aspect being shown. This condenser may be provided with posts 45 and fringes of wires 40 as illustrated in Figures 1 and 2.

Figures 8 and 9 illustrate another embodiment of the invention. As therein illustrated, the con-' refrigerant being supported on part of this central portion. This portion is elevated so as to provide a clearance of about an inch above the apex of the floor 6|. As indicated in Figure 9, the central portion of the condenser is divided by a longitudinal partition 65 and a transverse partition 66, both of these partitions being provided with perforations or apertures 6'! through which gas or vapor may freely pass. The partitions 65 and 66 aid in the distribution of condensate through the various portions of the condenser. The distribution is further carried out by means of guide members such as are illustrated'in Figure 9. Between each ceiling portion 62 and the adjacent floor portion 6| are inserted a number of guide elements 10 which may consist of pieces of wire bent to U-shape, the end of the U projecting beyond the upper edges of the ceiling portions 62. Between the upwardly projecting arms I! of these members are a number of short pieces of wire 12 laid side by side in spaced relation as shown. Below the member 10 are a pair of guiding members 13 extending from the partition 66 and the end walls of the condenser and upwardly bent as at 14. A second U-shaped guide member 15 is located below the members I4. This arrangem'ent is duplicated on each side of the partition 66 and under each ceiling portion 82. When the interior of the condenser is exhausted prior to scaling oif, the ceiling portions 62 are pressed by the atmosphere toward the adjacent portions of the floor 6 I these regions being prevented from collapsing completely by the presence of the uide members 10,-12, 13 and 15. When the condensate drips from the condensing surface 64, it is caught by the guide member 10 and forms a shallow pool therein between the floor and ceiling of the condenser. When the condensate in pool backs up to the ends of the arms II, it flows around these ends and is caught by the guide members 13 above which pools are formedwhich spill into the guide member I5. Hence, the secondary refrigerant is distributed over a large proportion of the floor area and is compelled to flow over this area in a zig-zag path, the motion of this thin film promoting heat transfer from the floor of the condenser to the liquid itself.

Figures 11 and 12 illustrate a condenser similar to that shown in Figure 1, this condenser being provided with a mechanical device for aiding in the uniform distribution of condensate which drips from the condensing surface 25. At the central point of the condensing surface 25 is mounted a pivot bearing 80, a corresponding bearing 8| being mounted on thefloor 23 immediately below the bearing 88. Mounted in these bearings is a light shaft 82 carrying a horizontal disk 83 which has a considerable number of perforations as at 8.4. Extending inwardly at an angle from the periphery of the disk 83 are a number of light vanes 85. These vanes preferably make equal angles with corresponding radii. When the temperature of the cabinet 2| is considerably above the desired temperature, there is a flow of heat of considerable magnitude through the condenser.

V This results in a rapid vaporization of the conthrough the perforations 84 from following the under surface of the disk to the edge thereof.

'It is obvious that many changes and modifications may be made in the apparatus herein shown and described and that many of the details are capableof being embodied in different but equivalent structure, without departing from the spirit or scope of the invention as defined by the following claims;

I claim 1. Apparatus for controlling the refrigerating effect of low temperature primary refrigerants on a refrigerator cabinet, which comprises a gastight condenser adapted to be supported in said cabinet, means for enclosing a quantity of primary refrigerant against a portion of the top of 25 said condenser, and a quantity of secondary refrigerant within said condenser such that substantially all said secondary refrigerant is congealed against the chilled ceiling of the com denser when the cabinet is at its desired equilibri' um temperature.

2. Apparatus for controlling the refrigerating effect of low temperature primary refrigerants on -a refrigerator cabinet, which comprises a gastight condenser adapted to be supported in said cabinet, means for supporting a quantity of primary refrigerant on a portion of the top of said condenser in eflicient heat exchanging relation thereto whereby a portion of the ceiling of the condenser is chilled to a low temperature, and a quantity of secondary refrigerant enclosed in said condenser, said condenser having a floor sloping away from a high point beneath the chilled portion of said ceiling.

3. Apparatus for controlling heat flow to a low temperature refrigerant, comprising a gas-tight box having a top portion adapted for direct contact with said refrigerant and a bottom adapted to be exposed to the interior of a refrigerator cabinet and sloping away from a high point,

away from a high point, a predetermined quan- C9 tity of secondary refrigerant sealed in said box for heat transfer from said bottom to said top portion byvaporization and condensation, and means on said top portion directly above the bottom portion adjacent to said high point for directing the drip of condensate formed thereon to said bottom portion therebelow.

5. Apparatus for controlling heat flow to a low temperature refrigerant, which comprises a gas-w tight box having a top portion adapted for contact} with said refrigerant and a bottom sloping away from a high point, means on said top for directing the drip of condensate formed on the inside surface thereof to the portion of the bottom adjacent to said high point, and means on said hot- 7 tom for promoting uniform distribution of said condensate thereover.

6. In apparatus for controlling heat flow to a low temperature refrigerant, a gas-tight box, a secondary refrigerant in said box adapted to transfer heat by vaporization against the floor of the box and condensation against the celling, and means on said floor for promoting uniform distribution of liquid thereover, said means comprising a layer of woven wire netting laid over a substantial portion of said floor and. means for holding said netting evenly against the surface of said floor.

7. In apparatus for controlling heat flow toa low temperature refrigerant, a gas-tight box having a quantity of secondary refrigerant therein for heat transfer by vaporization against the floor of the box and condensation against the ceiling of the box, and means on said ceiling for guiding the drip of condensate formed thereon, said means comprising rows of closely spaced wires supported by and projecting downwardly from said ceiling.

8. Apparatus for controlling heat flow to a low temperature refrigerant, comprising a gas-tight box having a portion of its top adapted for direct contact with said refrigerant, means substantially insulating said portion of the-top from the rest of the top, and a quantity of secondary refrigerant within the box for heat transfer to said portion of the top by vaporization and condensation.

9. In an apparatus for controlling heat flow to a low temperature refrigerant, a, receptacle for a block of said refrigerant, and means within said receptacle for supporting said block therein, said means comprising a series of parallel ribs on the bottom of the receptacle, some of said ribs having their upper portions wider than their lower portions.

10. In apparatus for controlling heat flow to a low temperature refrigerant, a gas-tight box having a portion of its top adapted to support said refrigerant, and means on said Prtion of the top for promoting intimate heat-transferring contact with said refrigerant, said means comprising a series of parallel ribs each having its upper portion wider than its lower portion.

11. In apparatus for controlling heat flow to a low temperature refrigerant, a gas-tight box having a portion of its top adapted to support said refrigerant and having a floor sloping away from a high point directly below said top portion, a quantity of secondary refrigerant in said box, and means for promoting uniform distribution of condensate from said top portion over said floor,

said means comprising a layer of wire netting covering a substantial portion of said floor, a layer of steel wool over said netting, a layer of netting over said wool, and a plurality of supporting, pillars secured at their upper ends to said ceiling and pressing with their lower ends on said netting and wool.

12. Apparatus for controlling heat flow to a low temperature refrigerant, comprising a gastight container having a portion of its top adapted for heat-exchanging relation with said refrigerant and a bottom sloping away from a high point, a quantity of secondary refrigerant within said container, and means on the bottom of said container for distributing thereover condensate dripping from said top portion, said means comprising barriers adapted to form series of shallow pools of condensate on said bottom.

13. Apparatus for controlling heat flow from the interior of a refrigerator cabinet to a low temperature refrigerant, comprising a gas-tight box within said cabinet having its bottom exposed to the air in said cabinet, means for promoting the transfer of heat from a portion of the top of said box to refrigerant thereon, and a quantity of secondary refrigerant within said box such that substantially all secondary refrigerant is in a congealed mass against the chilled portion of the ceiling of the box when the air in the cabinet is at the desired equilibrium temperature.

14. A method of preparing apparatus for controlling the refrigerating eifect of a low temperature refrigerant to maintain a refrigerator cabinet at a desired temperature, which comprises installing a gas-tight box in a cabinet, placing low temperature refrigerant in efficient heat-exchanging relation. with a portion of the top of said box, exhausting substantially all the air 20 from said box, introducing into said box a measured quantity of liquid having a freezing point below the temperature of primary refrigerant, noting the resulting equilibrium temperature of the air in said cabinet, adding successive 25 measured quantities of said liquid and noting corresponding equilibrium cabinet temperatures until a critical total is passed such that the further addition of liquid fails to lower the equilibrium cabinet temperature, removing said liquid from 30 said box, inserting in said box a quantity of freezable liquid having a freezing point suitably about the temperature of the primary refrigerant, the quantity of said freezable liquid being equal to said critical quantity plusa calculated amount for a minimum congealed layer on the chilled surface in said box.

15. That method of promoting the transfer of heat to a solidified gas refrigerant which comprises supporting said refrigerant upon a plurality of heat conducting surfaces and providing beheath some of said surfaces channels for the the distillation of a volatile liquid comprising a closed system having a portion exposed to a warmer region and a second portion in heat exchanging relation to a cooler region, and within said closed system a quantity of volatile liquid such that whenever said warmer region is at the desired temperature substantially all of said volatile liquid is in a congealed mass adjacent to said second portion of said closed system.

19. In combination in refrigerating apparatus a cake of solidified gas refrigerant, a surface adapted to support said cake, a plurality of metallic members protruding from said surface, and in the bottom of said cake channels underlying portions of. some of said metallic members.

WILLIAM F. hemp. 

